A lone wolf is any one person, or one small group of persons, suspected or blamed – rightly or wrongly – in the commission of the assassination of a heavily guarded political figure, or an act of mass murder.

Lee Harvey Oswald is the archetypical suspected lone wolf in Americancriminal history. The Warren Commission blamed him for the assassination of PresidentJohn F. Kennedy. But doubts persist to this day whether Oswald did, or even could have, engineered that assassination alone. Doubters point to the very low quality of his chosen weapon, and to the testimony of witnesses – now long-since dead, and conveniently so according to doubters – about gunfire coming from sources other than the sixth floor of the Texas School Book Depository overlooking Dealey Plaza in Dallas, Texas. Those same doubters, of course, name a large number of suspects, including Mafia don Sam Giancana and even Lyndon Baines Johnson, Kennedy's immediate successor.

In the aftermath of the September 11, 2001 attacks, the government of the United States refused to entertain the notion that those who carried out those attacks, did so in the name of Islam and in obedience to the foundational documents of that religion. Instead they identified Osama bin Laden as a type of lone wolf, and the group he founded (Al-Qaida, or "The Base" in Arabic) as a "lone wolf group," however illogical such a concept might sound. The presence in the Koran of the Arabic word for the English verb to fight, and repeated exhortations for "slay[ing]" the "infidels," belie this notion.

On 1 October 2017, a man named Stephen Pollack allegedly used multiple extra packs of ammunition to kill fifty-nine people, and wound more than 500 others, single-handedly. This, if true, would make him a lone wolf. But already, witnesses are alleging that the shots that killed or wounded those concertgoers at that venue came from more than one location.